Various implant-related devices and systems have been created in recent years in an effort to anchor dental prostheses more directly and flexibly in the mandible or maxilla than was possible using conventional dentures or bridges. Conventional implant approaches have typically employed a pre-manufactured coping or abutment which must be ground by the practitioner or the lab in order to angulate the prosthesis which respect to the implant axis. Obviously, such angulation is limited in systems which require that the screw coupling the prosthesis to the implant be inserted through a bore in the crown.
Such systems typically employ an anchor or "implant" which has been inserted into the bone and from which extends prosthesis-supporting structure typically coupled to the implant using a fixation screw or other desired fastener. All such systems have involved biologic and aesthetic compromises. Bacteria, food and other matter exacerbate corrosion, chronic infection and bone loss. Secure fixation to the implant often requires fasteners that extend from the crown and thus invasion sites for foreign materials as well as distraction to the patient. Conventional such systems also typically feature narrow emergence profiles from the gingival tissue (sometimes exposing metallic structure) which can cause visually and often phonetically adverse aesthetic complications.
To the extent that conventional implant abutment systems employ precision attachments, they do so in a narrow manner, primarily to secure prostheses such as bridges to copings on natural teeth or other anchors. Such attachments have not been conventionally employed to provide patient--removable prostheses, primarily because the abutment designs (usually featuring a central access bore) could or did not accommodate a precision attachment component within the contours of the abutment.
The following is a brief review of some of the conventional implant- and abutment-related references.
U.S. Pat. No. 5,116,225 issued to Riera ("Riera") discloses an angulated abutment system, a pair of bases which are adapted to fit together and with the implant to allow prostheses to be disposed at a large number of predetermined angles with respect to the implant, a screw for mounting the bases on the implant, and a two part abutment system which may be screwed on the bases so that structures supporting the crown may be disposed at various angles relative to the bases. The system thus apparently aims to provide great flexibility in lateral and vertical angulation of the prosthesis with respect to the implant. The Riera system allows for angulation correction in intervals as little as 6 degrees by using a series of six different parts that are sequentially attached ending with a gold cylinder or plastic sheath that, once cast or cast to, serves as the basis upon which the crown is to be built. This device features no means for preventing loosening of the fixation screw, and it requires the laboratory to maintain comprehensive inventories of plastic sheaths, cylinders and other angulated components. Furthermore, the components feature centrally disposed cylindrical bores which would impede inclusion of precision attachment devices for coupling crowns or other devices.
U.S. Pat. No. 5,106,299 issued to Ghalili ("Ghalili") discloses a dental implant system which includes an abutment adapted to connect to upper portions of an implant, held in place using a fixation screw, and upper portions of which are adapted to receive an insert which bears against the fixation screw and a spring loaded device to hold the insert in place so that the fixation screw does not loosen. The crown fits the abutment. The Ghalili abutment, because of its height, permits relatively little angulation of the crown from the implant axis. Furthermore, the central bore of the abutment would interfere with precision attachments or other connection devices for prostheses or crowns. Additionally, the Ghalili anti-rotational pin is exposed on the exterior of the crown, which can introduce hygiene problems, particularly when combined with the relatively complex spring-loaded mechanism of the pin.
U.S. Pat. No. 5,125,839 issued to Ingber ("Ingber") discloses an implant system that includes an abutment held in place on an implant via a fixation screw, and to which a crown may be attached. The fixation screw enters through the top of the crown, which may be filled using resin filler. The Ingber implant assembly, while it facilitates customized formation and fitting of dental prostheses, requires a central bore in the crown for the fixation screw which requires a dental filler and thus impedes aesthetic effects, durability, retrievability, and does not adequately address the issues of screw loosening. Additionally, the requirement of a central bore in the crown to accommodate the fixation screw dramatically limits angulation of the crown with respect l.o the implant axis.
U.S. Pat. No. 5,104,318 issued to Peshe ("Peshe") once again discloses an implant system which includes an abutment adapted for connection to an implant, with fixation screw for connecting the abutment to the implant, and a separate retainer screw for attaching the crown to the fixation screw and the abutment. The Peshe structure, with its conceptually similar fixation screw and abutment, together with crown bore, presents the same types of problems as Ingber.
U.S. Pat. Nos. 4,854,872 and 5,015,186 issued to Detsch (respectively, "Detsch 872" and "Detsch 186") disclose prosthetic implant attachment systems that include a base member having a lower end adapted to seat on the upper end of the implant, and an upper end of diameter corresponding to profiles of various teeth, a securing device for securing the base to the implant, and various straight and angled or variably angled prosthetic heads attached to the base for supporting the crown. The Detsch 186 attachment system once again features a crown with a centrally disposed bore through which a fixation screw must attach, with the concomitant flexibility, durability, aesthetic problems and screw loosening problems.
U.S. Pat. No. 4,713,003 issued to Symington et al. ("Symington") discloses a device for attaching a prosthesis to an implant. The device includes a fixation screw for insertion in the implant which in turn carries an abutment connected to the fixation screw by a second screw. The abutment may carry a prosthesis, and it may also attach to a prosthesis via a retaining screw received in a threaded cavity in upper portions of the abutment. The Symington system once again requires a centrally oriented bore in the crown.
U.S. Pat. No. 4,780,080 issued to Haris ("Haris") discloses an implant system formed of a root member implanted in the bone and carrying a post in which an angular stewed head may be mounted for supporting a crown. The Haris system relies heavily on dental cement and fails to control rotation of the base with respect to the implant.
U.S. Pat. No. 4,988,298 issued to Lazzara ("Lazzara 298") discloses a dental implant system that contains a precision machined abutment for attachment to an implant and which supports a crown, portions of which are attached to the abutment. U.S. Pat. No. 4,955,811 issued to Lazzara ("Lazzara 811") discloses a dental implant fixture that is non-rotatably connected to an implant and includes a two part impression coping that may be non-rotatably connected to the implant. U.S. Pat. No. 4,850,870 issued to Lazzara et al ("Lazzara 870") discloses various abutment posts and copings for use with implants. U.S. Pat. No. 4,856,994 issued to Lazzara et al ("Lazzara 994") discloses a healing cap for use in dental implantology during healing in gingival tissue. The Lazzara systems are state of the art, but their premanufactured nature impairs flexibility in conforming an abutment and a prosthesis to the gingiva in a manner and at proper angulation to replicate the look and feel of natural teeth.
U.S. Pat. No. 4,318,696 issued to Kasama ("Kasama") discloses an implant system featuring elastic material attached to the head of the implant, together with a crown attached to the elastic material. U.S. Pat. No. 5,033,962 issued to Scatena ("Scatena") discloses an implant system that includes a "stump" which features a lower part or base for connection to an implant, and an upper head which attaches to a cap via an elastic element. The cap supports a crown. The Kasama device correctly addresses the need in certain cases to replicate natural root/ligament-induced articulation in opposing elastic or flexible material between the crown and the implant. The Scatena device also includes an elastic element, but between a cap which supports the crown and a head which fits the implant. However, the Scatena structure appears to include no mechanism for preventing rotation between the head and the implant, and the elastic material is distanced from the bone.
U.S. Pat. Nos. 5,073,111, 5,035,619, and 5,145,372, issued to Daftary (respectively "Daftary 111", "Daftary 619" and "Daftary 372") disclose a system and method for implanting tooth analogues which include a standard implant and a cover screw which may be replaced with a healing cap for healing of the gingival tissue. The healing cap may then be removed and replaced by an abutment having an emergence profile matching that of the healing cap, which abutment is adapted to receive a crown. The Daftary 111 patent healing cap claims to provide frusto conical emergence profile in the gingival tissue more closely simulating that of a natural tooth. It unfortunately provides only a circular cross section gingival cuff, however, and various healing caps of various heights must be inventoried in order to accommodate differing gum thicknesses and desired emergence profile.